The present invention relates to heaters used to dispense air treatment chemicals, such as insect control agents, fragrances and deodorizers. More particularly, it relates to contact assemblies for carrying electricity to a heating element used therewith, and for then spreading the heat generated by the heating element around a dispensing wick.
A known type of air treatment chemical dispenser is that disclosed in U.S. Pat. No. 6,968,124, the disclosure of which is incorporated by reference. In this type of dispenser a liquid air treatment chemical is stored in a bottle. A wick dips into the liquid, and then extends upward out of the bottle. An upward end of the wick is surrounded by a ring-type electrical heater. Heating of the upward end of the wick causes air treatment chemical to be volatized from the wick, and thus the bottle, to the surrounding area.
One particularly desirable form of ring-type heater is one with a positive temperature coefficient “PTC” heating element. A PTC heating element is typically in the form of a pill-shaped tablet formed from pressed conductive granular material. Its resistivity to electrical charge generates heat, but that resistivity increases with an increase in temperature, thereby providing an inherent desirable control function against overheating.
A particularly desirable form of heater that uses a PTC heating element is the “All-Out” heater sold in India by Karamchand Appliances Pvt. Ltd. This product has a housing that is generally doughnut shaped, but hollow. A first ring-shaped electrical contact is positioned in the housing to extend around a central axial through bore, the bore being sized to receive the wick. One end of the contact connects to a prong of an external plug. At the other end there is a portion designed to abut a PTC type pill heating element.
On the other side of the PTC pill of the All-Out heater is placed a second ring-shaped electrical contact that also extends around the through bore. It has a connection to another external plug at one end. At the other end of the ring there is a portion designed to rest against an opposed side of the PTC pill. A top housing part is riveted to the lower housing part.
Electrical charge passes through the contacts of the All-Out heater to the pill, causing the pill to generate heat. The generated heat is then carried back along the contact to spread the heat around the through bore, and then to the wick. Heating of the wick facilitates volatilization of air treatment chemicals drawn up by the wick.
While this type of heater has many advantages, there are still a number of features in need of improvement. For example, because the two ring contacts are over each other in close proximity all the way around the ring, there is a theoretical potential for charge to be directed inefficiently if the parts are not precisely assembled. Further, the way some of the parts are installed inside the housing in the All-Out design is awkward, particularly with respect to insuring that small parts are properly aligned for optimal function. Also, the need to rivet the housing together adds cost and complexity.
Hence, a need exists for an improved heater for use with such volatile dispensers.